Python：在包模块中从主文件导入变量

Question

i try to use a complex structure in flask restfull, my structure is the following:

main.py
-models
-- __init__.py
--modelA.py
-resources
--__init__.py
--resourceA.py

I have a variable in main.py and i need this variable in models.modelA and i need also models.modelA in resources.resourceA. At this point everything is ok. When i start my app, i get the following error:

Traceback (most recent call last):
  File "main.py", line 12, in <module>
    from resources.resourceA import functionA
  File "/var/www/project/resources/resourceA.py", line 11, in <module>
    from models.modelA import *
  File "/var/www/project/models/modelA.py", line 8, in <module>
    from main import mainvariable
  File "/var/www/project/main.py", line 12, in <module>
    from resources.resourceA import functionA
ImportError: cannot import name functionA

I hope your help

Answer 1

What you basically have here is called a circular import. As the traceback states, your main module is importing functionA from resources.resourceA . And resourceA is importing models.modelA which is in turn trying to import main which again requires resources.resourceA .

Unless a particular order is resolved, python interpreter cannot understand how to resolve the modules. You can however solve this problem in an easier way.

If the models.modelA doesn't require a module level import for main , you can shift the import to the function / class scope where you need its imports.

See here for more on circular imports .